Known methods for separating and purifying a basic amino acid from a culture containing the basic amino acid and microbial cells using an ion exchange resin includes (1) a method in which after removing solid components such as microbial cells by centrifugation, condensing precipitation using a polymeric condensing precipitator or ultrafiltration and the like from the culture made acidic, a cell-free culture fluid is charged onto the top of a column filled with a strong acid cation exchange resin adjusted at pH0.5 to pH3.0 and then an eluent is charged onto the top of the column whereby separating and purifying the basic amino acid (Patent References 1 to 3 and the like), (2) a method in which a basic amino acid is separated using a weak acid cation exchange resin from a neutral aqueous solution containing several amino acids including the basic amino acid (Patent Reference 4) and (3) a method in which a culture containing microbial cells is charged onto the top of a column filled with a strong acid cation exchange resin to allow an amino acid to be adsorbed on the resin and then water is poured into the column backward via the bottom thereof to allow the cells depositing on the resin to float up and to be removed via the top of the column and then the amino acid is eluted (Patent Reference 5).
However, the abovementioned method (1) requires a pretreatment to remove the microbial cells from the culture before bringing the culture into contact with the ion exchange resin, and also requires an acidic pH of the culture which is 3 or lower for the purpose of removing the cells efficiently, and such a pH is not within the range of pH which allows the exchange by the weak acid ion exchange resin and the basic amino acid is adsorbed only weakly onto the weak acid ion exchange resin. Accordingly, it is not possible to separate the basic amino acid efficiently using the weak acid ion exchange resin from the acidic culture after removing the cells.
When applying the abovementioned method (2) after separating and removing the cells from the neutral culture containing the microbial cells, the purification yield is problematically poor because of poor separation of the cells in a neutral range.
Also in the abovementioned method (3), the amino acid purification efficiency is disadvantageously poor since the cells contained in the culture together with the amino acid are mostly deposited on the resin.
Patent Reference 1: Japanese Published Examined Patent Application No. 39516/1978
Patent Reference 2: Japanese Published Examined Patent Application No. 61272/1994
Patent Reference 3: Japanese Published Examined Patent Application No. 5050/1964
Patent Reference 4: U.S. Pat. No. 2,549,378
Patent Reference 5: Japanese Published Examined Patent Application No. 53509/1992